Steps to Reproduce:

1. Have JIRA + Confluence
2. Add user just to JIRA (jira-users)
3. Grant this user application access to Confluence. Let's say, update the same user and add him/her to Confluence (confluence-users)

Expected Results:

1. This user should show up in the People Directory on Confluence.

Actual Results:

1. This user is missing from People Directory on Confluence

Workaround:

1. Access this URL:

   https://<yourInstance>.atlassian.net/wiki/display/~<username>

Notes:
Documentation (Searching the People Directory) states that

The people directory includes anybody who has logged into Confluence or who has had a user account created for them in Confluence.